The invention relates to a device for changing the gear ratio on tools having a gear assembly with variable gear ratio and is especially applicable to portable tools of the type in which an output shaft from the motor is connected to a tool-bearing shaft by means of a sliding clutch.
In tools of this type, the clutch may be shifted between at least two positions in order to engage alternately with two or more gears which have different numbers of teeth and are driven by the motor shaft. The clutch is generally shifted by means of a control device actuated externally of the tool housing.
Various devices have been proposed which engage a gear cluster for moving the same between at least two positions for changing the gear ratio of the gear assembly. For example, U.S. Pat. No. 3,880,015 discloses a speed-changing device for effecting axial shifting of gears in a transmission assembly. The speed-changing device is fixedly mounted with the aid of screws into the wall of the gear-box housing. However, such devices require time for assembling the unit and for mounting in the gear-box wall.
Accordingly, it is an object of my invention to provide a device for changing the gear ratio in the gear assembly of a tool which is easily inserted into the wall of the gear-box housing without the need for additional fastening means. It is a further object of my invention to provide such a device which can be merely inserted by a snap action whereby the device is resiliently held within the gear-box housing. It is still another object of the invention to provide such a device which, in addition to being easily insertable, is also effective in preventing the lubricating fluid from flowing out of the gear-box housing.
It is still another object of the invention to provide such a device which can be manufactured at low cost.